Guide rolls of this type serve to permit the rolled wire or rod to be fed conveniently into the next pass of the rolling stands downstream of the guide rollers. The guide rollers are thus directed to the center of the pass and are positioned as close as possible to the rolls of the subsequent mill stand since apart from the high speeds with which the wire or rod of modern wire or rod rolling lines traverse the finished mill stands, in this section of the wire or rod rolling line, one must take into consideration narrow pass tolerances. The guide rollers must be able to engage as much as possible without play even oval shaped wire or rod cross sections in this part of the rolling line so as to prevent a tilting or twisting of the wire or rod in the respective pass. This is achieved by a corresponding setting of the pivotal displacement of the pivot arms which carry the guide rollers, usually in the form of double-arm levers which are braced by leaf springs.
The most important drawback of this roller guide arrangement is that with the guide rollers set for a predetermined average cross sectional size of the wire or rod as a consequence of the unavoidable cross sectional variations of the rolled wire or rod which is fed between the rollers, elevated pressure loading of the guide rollers and the rolled wire or rod always arises when the wire cross section exceeds the preset dimensions. In these cases, the guide rollers work mainly as additional rolling elements. As a result, not only do the tolerances of the wire cross section suffer but the bearings of the guide rollers and the guide rollers themselves are loaded beyond the usual magnitudes.
In addition because the guides tend to loosen up, when the rolled wire or rod passing through them has cross sectional dimensions which exceed the set dimensions, there is the danger that the wire will tend to tip or twist in the guide pass. This is especially the case with oval cross sections as to which the tolerances also are poorer. In extreme cases, the rolled wire or rod can become over-rolled.
These problems are increased when the wire or rod is to be dimensionally rolled in accordance with the so-called “free size rolling” system since there the finished cross section of the rolled wire is maintained in a very narrow range and different torque cross sections are rolled in one and the same rolling pass.